Lignin-based elastic material as well as preparation method and application thereof

Abstract

The invention discloses a lignin-based elastic material as well as a preparation method and application thereof. The preparation method comprises the following steps: carrying out click polymerization reaction on a binary alkynyl compound, polyethylene glycol, lignin and an organic base catalyst in an organic solvent to obtain a prepolymer solution; the prepolymer solution is poured into a mold, so that the organic solvent in the prepolymer solution is volatilized, and the lignin-based elastic material is prepared. The preparation method disclosed by the invention is simple, the raw materials are simple and easy to obtain, the lignin-based functional material can be prepared by performing high-value utilization on the biological papermaking waste lignin under mild conditions without inert gas protection, and the polymer has stable cross-linked network, thermal stability, excellent mechanical property and better photo-thermal property, and can be used for preparing the lignin-based functional material. The light-operated shape memory and light-operated remote lifting of heavy objects under laser can be realized, and because an olefin-ether bond generated by the ester alkyne monomer has good dynamic property, the light-operated shape memory has good degradability and biological friendliness.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer chemistry and materials science, and specifically relates to a lignin-based elastic material and a preparation method and application thereof. Background Art

[0002] Biorenewable materials have been widely used in low-cost reinforcement polymer composite applications. Polymer composites designed for different uses are mostly based on natural cellulose fibers. Along with these cellulose fibers, lignin is a promising alternative to traditional petrochemical-based reinforcement materials. Lignin, along with cellulose and hemicellulose, is one of the main components of natural polymers that provide strength and rigidity to plant roots and stems. Lignin is the most abundant byproduct of the paper industry and the second most abundant natural polymer on Earth after cellulose.

[0003] Lignin is a promising low-cost reinforcing material due to its biodegradable, carbon dioxide neutral, abundant presence in industrial waste, low cost, environmentally friendly, antioxidant, antibacterial and stable properties. Due to the above advantages, lignin-based polymer composites have broad development prospects as a new type of environmentally friendly and low-cost composite materials. Since the research on lignin or lignin-based polymer composites is still in its infancy, there are not many literatures on lignin-reinforced polymer composites. Based on the existing literature, lignin-reinforced polymer composites show bright prospects as a substitute for traditional synthetic fiber reinforced composites.

[0004] The chemical structure and physical properties of the starting lignin have a great influence on the thermal properties of these bio-based materials. Due to its aromatic-rich structure, lignin can generally improve the thermal stability of copolymers, blends and composites, and the rich hydroxyl structure in its structure provides the possibility of establishing intermolecular hydrogen bonds with polar polymers containing electronegative groups. This intermolecular interaction not only helps lignin to be compatible with polar synthetic polymers, but also affects the glass transition temperature of the material. In addition, modified materials using lignin can currently make great progress in the fields of battery energy storage, functional elastomers, biomedicine, photothermal evaporators, etc., which not only realizes the functional transformation of lignin, but also follows the design principles of sustainability, low cost and environmental protection.

[0005] Recent advances in the field of biopolymer processing are very promising for designing sustainable and low-cost materials. The current application of lignin mainly has problems such as complex synthesis methods, immature mass production processes, and poor reproducibility of some material properties. For example, Sun et al. combined thiol-ene click chemistry with silyl ether crosslinkers to prepare recyclable lignin-based thermosetting materials. The mechanical properties of lignin-based thermosetting materials are directly related to the ratio of crosslinker to lignin. Experimental results show that the tensile strength can reach 2.7MPa when the crosslinker is prepared with difunctional thiol and the lignin content is 11% (Tang, MBC, email protected, E. Email protected, et al. Mechanically Tunable and Reconstructable Lignin Thermosets via "Click" Chemistry and Surface Functionalization [J]. Macromolecules, 2023, 56 (7): 2831-2840.). Xu et al. prepared a series of lignin-based polyester thermosetting materials with adjustable properties by changing the ratio of lignin units, and used microwaves to extract lignin monomers and degrade and recycle them. Compared with natural lignin, the elongation at break of the lignin-based thermosetting resin prepared by solvent extraction combined with microwave extraction of lignin monomers has increased from 99% to more than 200%, and has better mechanical properties (Xu, Y., K. Odelius and M. Hakkarainen. Recyclable and flexible polyester thermosets derived from microwave-processed lignin [J]. ACS Applied Polymer Materials, 2020, 2 (5): 1917-1924.). Therefore, the next step in the development of lignin-based elastic materials needs to focus on the synthesis method, develop a more efficient and environmentally friendly synthesis process, and simplify the operation steps. At the same time, in terms of material design, more comprehensive considerations should be given to maximize the performance advantages of lignin. Summary of the invention

[0006] In order to overcome the shortcomings of the prior art, the present invention provides a lignin-based elastic material and a preparation method and application thereof. The preparation method is simple and efficient, the reaction raw materials are easily available, the reaction conditions are mild, and a lignin-based elastic material with excellent mechanical properties and good photothermal properties can be prepared without purification.

[0007] The specific technical solutions are as follows:

[0008] The present invention provides a method for preparing a lignin-based elastic material, comprising the following steps:

[0009] (1) subjecting a dibasic acetylenic compound represented by formula (I), polyethylene glycol, lignin represented by formula (II) and an organic base catalyst to a click polymerization reaction in an organic solvent to obtain a prepolymer solution;

[0010] (2) pouring the prepolymer solution into a mold to volatilize the organic solvent in the prepolymer solution, thereby preparing the lignin-based elastic material represented by formula (III);

[0011] The structural formula of the dibasic alkynyl compound is shown in formula (I):

[0012]

[0013] The structural formula of the lignin is shown in formula (II):

[0014]

[0015] The structure of the lignin-based elastic material is shown in formula (III):

[0016]

[0017] Wherein, R is a straight chain alkyl group.

[0018] The preparation method of the present invention utilizes a hydroxyl-alkyne click polymerization reaction to prepare a lignin-based elastic material with excellent mechanical properties and good photothermal properties in one pot. The preparation method can ensure that the prepared lignin-based elastic material has excellent mechanical properties and solid-solid phase change properties, and can be used to explore shape memory properties under laser.

[0019] Preferably, R is a straight-chain alkyl group having 1 to 30 carbon atoms (1, 2, 5, 10, 20, 30, etc.).

[0020] Preferably, in the click polymerization reaction system, the lignin represented by formula (II) is Shanghai Dongsheng lignin, brand LS-1.

[0021] The present invention introduces lignin from pulp and paper waste into a click polymerization reaction system as one of the hydroxyl source components, and prepares a lignin-based elastic material using a diacetylene compound, polyethylene glycol, lignin and an organic base catalyst as raw materials in a one-pot method. The introduction of lignin can make the lignin-based elastic material have a better cross-linking network, so that the material has excellent mechanical strength; and due to the natural photothermal properties of lignin, the prepared lignin-based elastic material absorbs energy under sunlight and laser and converts it into heat energy, thereby realizing the application of controllable shape memory under laser and remote lifting of heavy objects.

[0022] Preferably, the method for preparing the dibasic alkynyl compound as shown in formula (I) comprises the following steps:

[0023] Under an inert gas atmosphere, an alkynyl compound represented by formula (IV) and a dibasic hydroxy compound represented by formula (V) are subjected to an esterification reaction to prepare a dibasic alkynyl compound represented by formula (I);

[0024]

[0025] Wherein, R is a straight chain alkyl group.

[0026] More preferably, R is a straight-chain alkyl group having 1 to 30 carbon atoms (1, 2, 5, 10, 20, 30, etc.).

[0027] Further preferably, the inert gas atmosphere is a nitrogen atmosphere or an argon atmosphere, preferably a nitrogen atmosphere.

[0028] Preferably, the average number average molecular weight of the polyethylene glycol is 2000-20000. The molecular chain length of polyethylene glycol increases with the increase of molecular weight. The material synthesized by polyethylene glycol with a small molecular weight stores less calorific value and has better tensile properties, but is easily broken when stretched, and the molecular chain segment is short, the shaping effect is poor, and the shape memory effect under the laser is difficult to directly present; the material synthesized by polyethylene glycol with a high molecular weight stores more calorific value, has relatively good tensile strength and toughness, has a good shaping effect, and is better applied under the laser, but the molecular weight of polyethylene glycol cannot be too high, which will cause the mechanical properties to deteriorate. Therefore, it is necessary to select polyethylene glycol with relatively good heat storage properties and mechanical properties. After balancing the two, a polyethylene glycol molecular weight of 10,000 is selected for preparation under optimal conditions.

[0029] Preferably, the organic base catalyst is 1,4-diazabicyclo[2.2.2]octane, N-methylmorpholine, 4-dimethylaminopyridine, triisopropylamine, 1,8-diazabicyclo[5.4.0]undec-7-ene or quinine;

[0030] Preferably, the organic solvent is at least one of acetonitrile, tetrahydrofuran, dichloromethane, chloroform, dichloroethane, toluene, 1,4-dioxane, dimethyl sulfoxide and N,N-dimethylformamide.

[0031] Preferably, the temperature of the click polymerization reaction is room temperature, 25-28° C., and the time of the click polymerization reaction is 10-50 min.

[0032] More preferably, the click polymerization reaction time is 30 min.

[0033] Preferably, in the click polymerization reaction system, the molar ratio of the alkynyl group of the dibasic alkynyl compound shown in formula (I) to the total amount of hydroxyl groups of polyethylene glycol and lignin is 0.8:1-1.2; the concentration of the total amount of all dibasic alkynyl compounds, polyethylene glycol and lignin monomers in the organic solvent is 50-300 mg / mL, and the preferred monomer concentration is 175 mg / mL.

[0034] Preferably, in the click polymerization reaction system, the organic base catalyst accounts for 0.3-1.5 wt % of the total mass of the dibasic acetylenic compound, polyethylene glycol and lignin.

[0035] Further preferably, the organic base catalyst accounts for 0.9 wt % of the total mass of the dibasic acetylenic compound, polyethylene glycol and lignin.

[0036] Preferably, the mass of lignin shown in formula (II) accounts for 1-25wt% of the total mass of polyethylene glycol and lignin. If the content of lignin is too little, not only will the original structure cross-linked network be insufficiently formed, resulting in poor mechanical strength, but also poor photothermal effect; if the content of lignin is too much, the rigidity of the prepared lignin-based elastic material will be too large, the elastic modulus will be high, but the mechanical properties will decrease, and the mechanical strength will be poor. Therefore, a lignin content of 2%-10% is selected to balance the mechanical properties and photothermal properties, and finally a lignin content of 8% is selected for subsequent application exploration, and the relative mechanical properties and photothermal properties are relatively excellent.

[0037] The present invention also provides a lignin-based elastic material prepared by the preparation method of the lignin-based elastic material. The lignin-based elastic material has excellent mechanical properties, good photothermal properties, can maintain a solid state without leakage at the phase change temperature, has a good shape memory effect, and due to the introduction of natural photothermal material lignin, can be controlled and realize controllable shape memory characteristics by energy input under laser.

[0038] The present invention also provides the application of the lignin-based elastic material in photothermal aspects such as memory material, temperature response material or light response material. The lignin-based elastic material can be customized in shape to explore its controllable shape memory properties under laser and realize unidirectional shape memory; in addition, the prepared lignin-based elastic material has excellent mechanical properties and can realize remote lifting of heavy objects under laser.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] (1) The method of the present invention is simple and efficient, the reaction raw materials are easily available, the reaction conditions are mild, and it can be carried out at room temperature. It does not require high temperature and high pressure and large-scale instruments and equipment. The polymerization efficiency is high, and the lignin-based elastic material can be obtained without a purification step. The organic base catalyst used is low in price, easy to store and use, and has stable properties.

[0041] (2) The present invention utilizes the waste lignin generated in the pulping and papermaking process and makes high-value use of it to prepare the waste into the lignin-based elastic material. Due to the natural photothermal properties of lignin, there is no need to introduce photothermal molecules separately, making the reaction raw materials easier to obtain and the raw materials are also greener and healthier. In addition, the prepared lignin-based elastic material has good degradation properties and is biofriendly.

[0042] (3) The preparation process ratio of the lignin-based elastic material prepared by the present invention can relatively make the product have the best properties. When the lignin content is 2%, the tensile strength is only 8.71MPa; when the lignin content is higher, the tensile strength will decrease relatively. For example, when the lignin content is 10%, 15% and 20%, the tensile strength of the lignin-based elastic material is 21.08MPa, 22.99MPa and 22.72MPa respectively, and when the lignin content is 20%, the elongation at break decreases to less than 200%. Among them, the mechanical strength of 4%, 6% and 8% is relatively good, the tensile strength is above 26MPa, and the elongation at break is above 600%. That is, the mass fraction ratio of lignin to PEG is 4:96, and the PEG segment is 10000, the mechanical properties are the best, and the tensile strength and elongation at break are 31.93MPa and 845% respectively. In order to balance the photothermal effect and the mechanical strength of the material, 8% lignin was selected for subsequent applications.

[0043] (4) The lignin-based elastic material prepared by the present invention has excellent mechanical properties, which can surpass most of the lignin-based elastic materials reported in the literature. It has a good photothermal effect and can realize the application of controllable shape memory under laser and light-controlled remote lifting of heavy objects. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a schematic diagram of lignin, PEG, and dibasic alkynyl compounds of the present invention, a preparation process of the lignin-based elastic material between the components, and a schematic diagram of the internal bonding of the final lignin-based elastic material.

[0045] Figure 2 This is the infrared spectra of lignin, PEG-10K, dibasic acetylenic compound and lignin-based elastic material 8%-Lignin-PEG-10K in Example 1.

[0046] Figure 3This is the thermogravimetric curve of the lignin-based elastic material 8%-Lignin-PEG-10K in Example 1.

[0047] Figure 4 This is the tensile curve of the lignin-based elastic material 8%-Lignin-PEG-10K in Example 1.

[0048] Figure 5 This is the cyclic tensile curve of the lignin-based elastic material 8%-Lignin-PEG-10K in Example 1 under 300% strain.

[0049] Figure 6 This is the step-by-step loading tensile curve of the lignin-based elastic material 8%-Lignin-PEG-10K in Example 1.

[0050] Figure 7 It is a curve diagram of the temperature rise of the sample of the lignin-based elastic material 8%-Lignin-PEG-10K in Example 1 when irradiated with simulated sunlight, and a comparison diagram of the final temperature of the material at different powers.

[0051] Figure 8 It is a curve diagram of the temperature rise of the lignin-based elastic material 8%-Lignin-PEG-10K in Example 1 when the sample is irradiated with a laser of 808nm and a comparison diagram of the final temperature of the material at different powers.

[0052] Fig. 9 This is the shape memory display process of the lignin-based elastic material 8%-Lignin-PEG-10K in Example 1 under 808 nm laser.

[0053] Fig.10 This is a demonstration process of the light-controlled remote lifting of heavy objects by the lignin-based elastic material 8%-Lignin-PEG-10K in Example 1 under 808nm laser.

[0054] Fig.11 This is the degradation process of the lignin-based elastic material 8%-Lignin-PEG-10K in Example 1 under acidic conditions. DETAILED DESCRIPTION

[0055] The present invention will be further described in detail below in conjunction with specific embodiments and drawings, but the embodiments of the present invention are not limited thereto. For process parameters not particularly noted, conventional techniques may be used.

[0056] In the embodiment, the dibasic alkynyl compound 1 is synthesized from propiolic acid and dihydroxyhexane according to the synthesis method in the published literature (Polym. Chem., 2012, 3(4): 1075-1083) under a nitrogen atmosphere. The synthesis route is as follows:

[0057]

[0058] The specific synthesis steps are:

[0059] In a 250mL two-necked flask equipped with a stirring magnet, a reflux condenser and a Dean-Stark separator, 1,6-hexanediol (3.54g, 30mmol), p-toluenesulfonic acid (1.03g, 6mmol) and 100mL toluene were added in sequence, and magnetic stirring was turned on. Then propiolic acid (5.6mL, 90mmol) was added dropwise to the stirred solution. After all the propiolic acid was added, the temperature was raised to 110°C and refluxed for 18h. After the end, the solution temperature was lowered to room temperature and the toluene was removed by rotary evaporation. The remaining oil was washed with dichloromethane and water, and the organic phase was collected, dried with anhydrous magnesium sulfate and filtered. The collected filtrate was rotary evaporated to remove the solvent, and a mixed solvent of petroleum ether and ethyl acetate (10:1, v / v) was used as the eluent. 5.24g of white crystals (2-1a) were obtained by chromatographic column separation with a yield of 79%.

[0060] Example 1

[0061] In this embodiment, the synthesis route of the lignin-based elastic material Lignin-PEG10K is as follows:

[0062]

[0063] PEG-10K (1281.3 mg), lignin (LS-1, 111.4 mg) from Shanghai Dongsheng Company, a dialkynyl compound (125.8 mg) and 9 mL of ultra-dry tetrahydrofuran were added to a glass bottle, and the glass bottle was placed in a 60°C water bath and stirred for 3 min until the polyethylene glycol (PEG-10K, number average molecular weight of 10,000) was completely dissolved. The glass bottle was then naturally cooled to room temperature, and the organic base 1,4-diazabicyclo[2.2.2]octane DABCO (13.7 mg) was dissolved in 9 mL of ultra-dry tetrahydrofuran and added to the reaction system through a microinjector. The molar ratio of the total hydroxyl group of polyethylene glycol and lignin to the triple bond of the dialkynyl compound in the system was 1:0.8, and the organic base catalyst accounted for 0.9 wt% of the total mass of the reaction system (total mass of lignin, dialkynyl compound, and polyethylene glycol). After adding DABCO and stirring, the product solution was poured into a square polytetrafluoroethylene mold after reacting for 0.5 h at room temperature and sealed with aluminum foil. After evaporation at room temperature for 3 days, a dark brown, opaque, flexible lignin-based elastic material 8% Lignin-PEG-10K was obtained.

[0064] Example 2

[0065] In this embodiment, lignin, as a natural photothermal material, has non-toxic, harmless and environmentally friendly characteristics, and the unique three-dimensional network structure of lignin provides a rigid skeleton of lignin-based elastic materials; by changing the mass ratio of lignin and PEG (the total mass remains unchanged), the mechanical properties of the obtained lignin-based elastic material can be adjusted, wherein the mass ratio of lignin and PEG is adjusted from 1:99 to 1:3, and the mechanical properties have also changed greatly, from being very easy to break to being a relatively tough material (see Table 1, the lignin content of 2wt% is very easy to break, while the relative strength and toughness of the lignin content of 4wt% are very good). The molar ratio of the total hydroxyl group of polyethylene glycol and lignin and the triple bond of the dibasic alkynyl compound in the system is 1:0.8, the organic base catalyst accounts for 0.9wt% of the total mass of the reaction system (the total mass of lignin, dibasic alkynyl compound, and polyethylene glycol), and the other parameters and methods are the same as in Example 1 to obtain a lignin-based elastic material.

[0066] Example 3

[0067] The polyethylene glycol in Example 1 was replaced with polyethylene glycol having an average number average molecular weight of 2000, the organic base catalyst was replaced with 4-dimethylaminopyridine, the organic solvent was replaced with dimethyl sulfoxide, the molar ratio of the total hydroxyl groups of polyethylene glycol and lignin and the triple bonds of the dibasic alkynyl compound in the system was 1:0.8, the organic base catalyst accounted for 0.9wt% of the total mass of the reaction system (total mass of lignin, dibasic alkynyl compound, polyethylene glycol), and other parameters and methods were the same as in Example 1 to obtain a lignin-based elastic material.

[0068] Example 4

[0069] The polyethylene glycol in Example 1 was replaced with polyethylene glycol having an average number average molecular weight of 4000, and the organic base catalyst was replaced with triisopropylamine, and the organic solvent was replaced with 1,4-dioxane. The molar ratio of the total hydroxyl groups of the polyethylene glycol and the dibasic alkynyl compound to the triple bonds of the polyethylene glycol and the dibasic alkynyl compound in the system was 1:0.8, the organic base catalyst accounted for 0.9wt% of the total mass of the reaction system (the total mass of the lignin, the dibasic alkynyl compound, and the polyethylene glycol), and the other parameters and methods were the same as those in Example 1, to obtain a lignin-based elastic material.

[0070] Example 5

[0071] The polyethylene glycol in Example 1 was replaced with polyethylene glycol having an average number average molecular weight of 6000, and the organic base catalyst was replaced with quinine, and the organic solvent was replaced with chloroform. The molar ratio of the total hydroxyl groups of the polyethylene glycol and lignin to the triple bonds of the dibasic alkynyl compound in the system was 1:0.8, the organic base catalyst accounted for 0.9wt% of the total mass of the reaction system (total mass of lignin, dibasic alkynyl compound, polyethylene glycol), and other parameters and methods were the same as in Example 1, to obtain a lignin-based elastic material.

[0072] Example 6

[0073] The polyethylene glycol in Example 1 was replaced with polyethylene glycol having an average number average molecular weight of 8000, the organic base catalyst was replaced with N-methylmorpholine, and the organic solvent was replaced with N,N-dimethylformamide. The molar ratio of the total hydroxyl groups of polyethylene glycol and lignin to the triple bonds of the dibasic alkynyl compound in the system was 1:0.8, the organic base catalyst accounted for 0.9wt% of the total mass of the reaction system (total mass of lignin, dibasic alkynyl compound, polyethylene glycol), and other parameters and methods were the same as in Example 1, to obtain a lignin-based elastic material.

[0074] Example 7

[0075] The polyethylene glycol in Example 1 was replaced with polyethylene glycol having an average number average molecular weight of 10,000, and the organic base catalyst was replaced with N-methylmorpholine, and the organic solvent was replaced with N,N-dimethylformamide. The molar ratio of the total hydroxyl groups of the polyethylene glycol and the dibasic alkynyl compound to the triple bonds of the polyethylene glycol and the lignin in the system was 1:0.8, the organic base catalyst accounted for 0.9 wt% of the total mass of the reaction system (the total mass of the lignin, the dibasic alkynyl compound, and the polyethylene glycol), and the other parameters and methods were the same as those in Example 1, to obtain a lignin-based elastic material.

[0076] Example 8

[0077] The polyethylene glycol in Example 1 was replaced with polyethylene glycol having an average number average molecular weight of 20,000, and the organic base catalyst was replaced with N-methylmorpholine, and the organic solvent was replaced with N,N-dimethylformamide. The molar ratio of the total hydroxyl group of polyethylene glycol and lignin to the triple bond of the dibasic alkynyl compound in the system was 1:0.8, the organic base catalyst accounted for 0.9wt% of the total mass of the reaction system (the total mass of lignin, dibasic alkynyl compound, polyethylene glycol), and other parameters and methods were the same as in Example 1, to obtain a lignin-based elastic material.

[0078] Sample analysis

[0079] Figure 1 The figure is a schematic diagram of lignin, PEG, and a dibasic alkynyl compound of the present invention, a preparation process of the lignin-based elastic material between the components, and a schematic diagram of the internal bonding of the final lignin-based elastic material. Since the total number of hydroxyl groups of lignin and polyethylene glycol is excessive, the prepared lignin-based elastic material has hydroxyl groups and olefinic ether bonds, so a lignin-based elastic material with a double cross-linked network of both covalent dynamic bonds and non-covalent hydrogen bonds is formed, so that the mechanical strength of the material is enhanced.

[0080] Figure 2] are infrared spectra of lignin, PEG-10K, dibasic acetylenic compound and lignin-based elastic material 8%-Lignin-PEG-10K in Example 1. The disappearance of the triple bond peak proves the successful synthesis of the lignin-based elastic material in Example 1.

[0081] Figure 3 This is the thermogravimetric curve of the lignin-based elastic material 8%-Lignin-PEG-10K in Example 1, which proves that the material has a good thermal decomposition temperature of 372°C. The higher decomposition temperature is conducive to subsequent photothermal testing and applications under photothermal conditions.

[0082] Table 1

[0083]

[0084] Figure 4 This is the tensile curve of the lignin-based elastic material 8%-Lignin-PEG-10K in Example 1. 8%-Lignin-PEG-10K has a significant stress-strain curve of a crystalline polymer. PEG-10K provides a flexible segment, and lignin provides a rigid segment. The soft and hard segments regulate the mechanical properties of the material. The tensile strength and elongation at break of 8%-Lignin-PEG-10k are 26.51 MPa and 603.54%, respectively, and it has excellent mechanical properties.

[0085] Figure 5 This is the cyclic tensile curve of the lignin-based elastic material 8%-Lignin-PEG-10K in Example 1 at 300% strain, which proves that it has good cyclic stability during the stretching process, which is beneficial to the subsequent shaping of property memory under light and heat.

[0086] Figure 6 This is the step-by-step loading tensile curve of the lignin-based elastic material 8%-Lignin-PEG-10K in Example 1. As the strain increases, the tensile stress increases continuously, and there is a certain tensile enhancement effect, which proves that the material has excellent mechanical properties.

[0087] Figure 7 The following is a graph showing the temperature rise of the sample of the lignin-based elastic material 8%-Lignin-PEG-10K in Example 1 when irradiated with simulated sunlight and a comparison of the final temperature of the material at different powers. The specific operation steps are to cut the lignin-based elastic material 8%-Lignin-PEG-10K in Example 1 into squares and irradiate the sample with 100 mW / cm 2 , 200mW / cm 2 、300mW / cm 2 , 400mW / cm 2 , 500mW / cm2 、600mW / cm 2 、700mW / cm 2 and 800mW / cm 2 The sample was irradiated under simulated sunlight for 5 minutes, and the simulated sunlight source was turned off after 5 minutes to observe and monitor the temperature change on the surface of the material. From the curve results, it can be clearly concluded that the material has obvious power dependence, and there is an obvious heat absorption and release platform during the heating and cooling process, which also proves that the lignin-based elastic material has certain heat storage performance.

[0088] Figure 8 The temperature rise curve of the sample of lignin-based elastic material 8%-Lignin-PEG-10K in Example 1 under 808nm laser irradiation and the comparison of the final temperature of the material under different powers are shown in the figure. The specific operation steps are to cut the lignin-based elastic material 8%-Lignin-PEG-10K in Example 1 into squares, respectively, at 200mW / cm 2 , 400mW / cm 2 、600mW / cm 2 、800mW / cm 2 , 1000mW / cm 2 and 1200mW / cm 2 The sample was irradiated with a laser power of 5 minutes, and the simulated laser light source was turned off after 5 minutes to observe and monitor the temperature change on the surface of the material. This also proves that the material has good laser power dependence and good photothermal properties.

[0089] Fig. 9 This is the shape memory display process of the lignin-based elastic material 8%-Lignin-PEG-10K in Example 1 under 808nm laser. Fig. 9 The material is formed in a petal-shaped mold to obtain a petal-shaped lignin-based elastic material, and the material is shaped at high temperature so that the petals are closed. After naturally cooling to room temperature, the petals remain in a closed state; at 800mW / cm 2 Under the irradiation of 808nm laser, the folded petals will return to their original shape under the light drive and open.

[0090] Fig.10 This is the demonstration process of the light-controlled remote lifting of a heavy object by the lignin-based elastic material 8%-Lignin-PEG-10K in Example 1 under 808nm laser. The lignin-based elastic material is first cut into long strips, pre-stretched on a tensile testing machine at room temperature to make the material have a certain length, and then a weight with a certain weight is hung on the sample; at 800mW / cm 2Under the irradiation of 808nm laser, the sample shrinks and returns to its original shape, lifting the heavy object, realizing the process of light-controlled remote lifting of the heavy object.

[0091] Fig.11 This is the degradation process of the lignin-based elastic material 8%-Lignin-PEG-10K in Example 1 under acidic conditions. Fig.11 A in the figure is a tetrahydrofuran solution in which concentrated hydrochloric acid (the amount of 37 wt% concentrated hydrochloric acid is 2 drops / mL) is added dropwise at room temperature, and the degradation is complete after 24 hours; Fig.11 B was subjected to acid degradation at 60°C (the amount of 37 wt% concentrated hydrochloric acid was 2 drops / mL), and it only took 4 hours to be completely degraded.

[0092] The above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A method for preparing a lignin-based elastic material, characterized in that: The following steps are involved: (1) subjecting a dibasic acetylenic compound, polyethylene glycol, lignin and an organic base catalyst to a click polymerization reaction in an organic solvent to obtain a prepolymer solution; (2) pouring the prepolymer solution into a mold to volatilize the organic solvent in the prepolymer solution, thereby preparing the lignin-based elastic material; The structural formula of the dibasic alkynyl compound is shown in formula (I): The structural formula of the lignin is shown in formula (II): The structure of the lignin-based elastic material is shown in formula (III): Wherein, R is a straight chain alkyl group.

2. The method for preparing a lignin-based elastic material according to claim 1, characterized in that: The lignin is Shanghai Dongsheng lignin; R is a straight-chain alkyl group having 1 to 30 carbon atoms.

3. The method for preparing a lignin-based elastic material according to claim 1, characterized in that: The preparation method of the dibasic alkynyl compound comprises the following steps: Under an inert gas atmosphere, an alkynyl compound represented by formula (IV) and a dibasic hydroxy compound represented by formula (V) are subjected to an esterification reaction to prepare a dibasic alkynyl compound represented by formula (I); Wherein, R is a straight chain alkyl group; The inert gas atmosphere is a nitrogen atmosphere or an argon atmosphere.

4. The method for preparing a lignin-based elastic material according to claim 1, characterized in that: The average number average molecular weight of the polyethylene glycol is 2000-20000.

5. The method for preparing a lignin-based elastic material according to claim 1, characterized in that: The organic base catalyst is 1,4-diazabicyclo[2.2.2]octane, N-methylmorpholine, 4-dimethylaminopyridine, triisopropylamine, 1,8-diazabicyclo[5.4.0]undec-7-ene or quinine; The organic solvent is at least one of acetonitrile, tetrahydrofuran, dichloromethane, chloroform, dichloroethane, toluene, 1,4-dioxane, dimethyl sulfoxide and N,N-dimethylformamide.

6. The method for preparing a lignin-based elastic material according to claim 1, characterized in that: The temperature of the click polymerization reaction is room temperature, 25° C.-28° C., and the time of the click polymerization reaction is 10-50 min.

7. The method for preparing a lignin-based elastic material according to claim 1, characterized in that: The molar ratio of the alkynyl group of the dibasic alkynyl compound to the total amount of hydroxyl groups of polyethylene glycol and lignin is 0.8:1-1.2; the concentration of the total amount of the dibasic alkynyl compound, polyethylene glycol and lignin in the organic solvent is 50-300 mg / mL; and the organic base catalyst accounts for 0.3-1.5wt% of the total mass of the dibasic alkynyl compound, polyethylene glycol and lignin.

8. The method for preparing a lignin-based elastic material according to claim 1, characterized in that: The mass of the lignin accounts for 1%-25% of the total mass of the polyethylene glycol and the lignin.

9. The lignin-based elastic material obtained by the preparation method according to any one of claims 1 to 8.

10. Use of the lignin-based elastic material according to claim 9 as a memory material, a temperature-responsive material or a light-responsive material.

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